On an air interface, user equipment (UE) has two radio resource control (RRC) statuses: an idle state and a connected state. When the UE needs to perform service transmission, the UE first needs to set up a connection to a network side device, that is, RRC connection setup, and the UE enters a connected state from an idle state, and then transmits service data. When the UE completes service data transmission, if the UE in a connected state does not transmit data for a long time, an inactivity timer expires, and the UE needs to release the RRC connection to the network side device, that is, RRC connection release, and the UE enters an idle state from a connected state. When downlink data arrives or uplink data arrives, the UE needs to set up an RRC connection again. After data transmission is completed, if the UE does not transmit data for a long time, the inactivity timer expires, and the UE needs to release the RRC connection. Therefore, in a process of switching an air interface state of the UE, that is, in a process of switching between an idle state and a connected state, a large quantity of signaling overheads are generated.
Cellular Internet of Things (CIoT) is a new technology based on a Long Term Evolution (LTE) system. A requirement of the cellular Internet of Things for a data rate is not high, and therefore, the cellular Internet of Things can provide a larger coverage gain and connection capability. In the CIoT, a huge quantity of terminals mainly perform small-sized packet transmission, that is, data packets transmitted by the terminals are relatively small. As communication requirements frequently increase and a quantity of terminals increases, a quantity of signaling overheads generated in RRC connection setup and RRC connection release significantly increases, and a network side device also needs more processing resources to process the control signaling. As a result, the network side device is overloaded.
In the prior art, there is a method for reducing RRC signaling overheads in an RRC connection setup process for UE and an eNB. Specifically, after an RRC connection is released, the UE and the eNB still reserve context information of the UE. When downlink data arrives or uplink data arrives, the UE needs to enter a connected state again, and the UE and the eNB separately use the stored context information of the UE to set up an RRC connection. In a process of setting up the RRC connection between the UE and the eNB by using the method, operations such as security activation and bearer setup do not need to be performed again, thereby reducing signaling overheads in the RRC connection setup process, and reducing network load. After the UE completes data transmission, if the UE does not transmit data for a long time, an inactivity timer expires, and the UE releases the RRC connection, and stores context information of the current connection. However, a large quantity of signaling overheads are still caused in an RRC connection release process.